HSC Survey Results

Scots Bay Survey # 7 Results from 29/07/2024

Survey Details

4 commercial purse seiners conducted this fishing survey on 29/07/2024 starting at 21:00:00, which was 1.78 hours after hide tide.

All vessels ran two transects each in the Main Survey Box.

There was a plankton tow and replicate conducted and CTD cast by Lady Janice II.

No tags were applied during this survey.

Samples were obtained for target strength estimation.

Tides Tables

Tide Schedule for Margaretsville NS, Station #315m Source: www.waterlevels.gc.ca

Acoustic Equipment

Each vessel was equipped with a Simrad ES38-18/200-18C combi (2-in-1) transducer prior to the survey that contains a 38kHz split beam and 200 kHz single beam transducer. Data was logged to the computer hard-drive for post-processing. All participating boats were calibrated on 38kHz before the survey.

Survey Results

Main Results

The results are subject to change as DFO will re-evaluate data editing, area estimation and apply a target strength.

Preliminary biomass prediction for Scots Bay using standardized parallel transects is 32,655mt, and with turnover applied 32,016mt.

Transect Details

Table 1: Transect Details
Vessel Transect # Date/Time Start Date/Time End Start Lon Start Lat End Lon End Lat Location Distance (km) Speed
BP T01 2024-07-29 19:45:33 2024-07-29 22:48:46 -65.243 45.032 -64.745 45.195 SB 43.22 7.64
BP T02 2024-07-29 23:12:01 2024-07-30 01:11:51 -64.759 45.249 -65.194 45.102 SB 37.95 10.26
FM T01 2024-07-29 21:23:09 2024-07-30 00:27:14 -65.231 45.062 -64.765 45.218 SB 40.99 7.21
FM T02 2024-07-30 00:48:41 2024-07-30 02:52:48 -64.786 45.270 -65.209 45.123 SB 37.23 9.72
LJ T01 2024-07-29 20:22:17 2024-07-30 00:02:38 -65.238 45.048 -64.698 45.225 SB 46.98 6.91
LJ T02 2024-07-30 00:23:08 2024-07-30 02:55:43 -64.755 45.265 -65.233 45.103 SB 41.69 8.85
MS T01 2024-07-29 20:19:15 2024-07-30 00:18:01 -65.234 45.076 -64.725 45.245 SB 49.32 6.69
MS T02 2024-07-30 00:40:59 2024-07-30 03:02:32 -64.787 45.284 -65.201 45.141 SB 37.69 8.63

Survey Summary

Table 2: Acoustic Survey Results
Vessel Transect No.  Target Strength (db/kg) Mean Sa (/m2) Biomass Density (kg/m2)
BP T01 -35.5 -43.905 0.144
FM T01 -35.5 -44.048 0.140
LJ T01 -35.5 -44.828 0.117
MS T01 -35.5 -46.807 0.074
FM T02 -35.5 -53.365 0.016
MS T02 -35.5 -54.611 0.012
BP T02 -35.5 -54.651 0.012
LJ T02 -35.5 -55.223 0.011
Note:
Transects are listed from greatest to least backscatter.
Table 3: Survey Summary Table
Layer Target Strength Area (km2) Mean Sa Density (kg/m2) Biomass (tons) Percent Area Percent Biomass Standard Error (tons) Standard Error (%)
Main Box -35.5 474 -47.1194 0.0658 32,654.99 100 100 10,122.87 31

Greatest Biomass Densities

A snip from the transect with the greatest biomass density (kg/m2)

A snip from the transect with the greatest biomass density (kg/m2)

The single point with the largest biomass density (kg/m2) was recorded by FM, at the following location:

The transect with the greatest average biomass density (kg/m2) was recorded by BP, at the following location:

Annual Summaries

Table 4: Annual Comparison Table
Current Year
Previous Year
Ground Survey Number Survey Date HSC Estimate HSC Turnover Adjusted Survey Date HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
Scots Bay 1 2024-05-05 78,662 78,662 2023-05-22 40,856.000 40,856 47,629 47,629
Scots Bay 2 2024-05-20 29,842 17,255 2023-06-06 113,767.329 108,783 98,582 92,772
Scots Bay 3 2024-06-02 93,804 89,523 2023-06-18 34,279.387 15,158 29,417 12,720
Scots Bay 4 2024-06-16 33,347 22,278 2023-07-02 11,744.776 5,113 9,330 3,622
Scots Bay 5 2024-07-01 7,252 3,123 2023-07-16 19,282.634 17,575 17,387 16,022
Scots Bay 6 2024-07-15 4,539 3,560 2023-07-30 4,549.933 1,904 3,474 1,093
Scots Bay 7 2024-07-29 32,655 32,016 2023-08-13 4,298.806 3,616 2,777 2,247
Scots Bay 9 NA NA NA 2023-09-10 3,053.669 2,916 3,219 0
Scots Bay 10 NA NA NA 2023-09-24 3,419.932 2,997 2,318 0
Scots Bay 8 NA NA NA 2023-08-27 2,896.659 2,300 1,612 1,224
Scots Bay 11 NA NA NA 2023-10-09 3,387.515 2,971 2,521 0
Table 5: Annual Summary Table
Year Ground HSC Estimate HSC Turnover Adjusted DFO Estimate DFO Turnover Adjusted
2023 Scots Bay 241,536.6 204,189 218,266 177,329
2024 Scots Bay 280,101.0 246,417 NA NA

Plankton, and CTD Data

Summary map

Plankton Data

Tow Summary Table

Tow 1
Tow 2
Base Details
Vessel Lady Janice II Lady Janice II
Set Number SB2024-11 SB2024-12
Ground SB SB
Date 29/07/2024 29/07/2024
Wind Direction (km/h) W W
Swell (m) 0.5 0.5
Air Temp (c) 22 22
Tow Details
Tow Start 19:04:00 19:21:00
Tow End 19:14:00 19:31:00
Start Lat 45.05817 45.05200
End Lat 45.05433 45.05283
Start Lon -65.19433 -65.20250
End Lon -65.20217 -65.21200
Avg Tow Depth (m) 1.730536 1.441772
Speed NA NA
Heading NA NA
Tide Direction against against
Other Data Collection
Flow Start 157440 199550
Flow End 199550 236886
No. Revolutions 42110 37336
Distance (m) 1131.622 1003.330
Volume 3554.991 3151.962
Secchi Disappear (m) 7 7
Secchi Reappear (m) 6 6

Tow Depth Profiles

Plankton tow depth profile #1

Plankton tow depth profile #1

Plankton tow depth profile #2

Plankton tow depth profile #2

The first tow is SB2024-11, which was against the tide and had an average depth of 1.7305365m. The second tow is SB2024-12, which was against the tide and had an average depth of 1.4417725m.

Captured plankton

Captured plankton from the surface tows

Captured plankton from the surface tows

CTD Data

CTD depth profiles for all 2024 Scots Bay surveys so far.

Sea surface temperatures

Annual average sea surface temperatures (SST) for Scots Bay.

Vessel Performance

Speed

Average vessel speed was 8.24. This is above the 8 knot requirement; vessels are urged to slow down to prevent backscatter noise from interfering with the acoustic data.

Distance

More than 2km of distance was cut from the planned lines; vessels are reminded to complete their assigned lines straight and without deviating or cutting corners short.